Hybrid high-power microwave-frequency integrated circuit

ABSTRACT

In a power microwave hybrid integrated circuit, a depth of recesses (2) in a metal base (1) is selected so that a face surface of chips (3) and a metal base (1) are coplanar, a dielectric board (5) has a shield ground metallization (10) on its back side at the places adjoining the metal base (1), the metal base (1) is sealingly joined and electrically connected to the shield grounding metallization (10) of the board (5), and interconnecting holes (7) of the board (5) are filled with an electrically conducting material (9), the spacing between the side surfaces of the chips (3) and the side surfaces of the recesses (2) in the base (1) being of 0.001 to 0.2 mm.

FIELD OF THE INVENTION

The present invention relates in general to electronic engineering andmore specifically to a power microwave hybrid integrated circuit.

BACKGROUND OF THE INVENTION

One prior-art power microwave hybrid integrated circuit is known, thecircuit comprises a metal base having through holes for nakedsemiconductor chips and an insulating polymer film joined to the metalbase and having through holes mating with those of the base. A secondinsulating film is placed on and held to the first insulating film, saidsecond film having through holes of a smaller size mating with the holesin the first polymer film. The naked semiconductor chips are mounted onthe back side of the second polymer film with their bonding pads towardsthe films (i.e., upwards). A second commutation level is arranged on theface side of the second polymer film and is electrically connected tothe chip bonding pads through the holes in the second polymer film (JP,B. 57-036746).

The integrated circuit discussed above is possessed of a low heatdissipation rate due to a small chip-to-metal base heat contact area.

One more prior-art power microwave hybrid integrated circuit is known,the circuit comprises a metal base having recesses, naked semiconductorchips disposed in and fixed to said recesses with a binder, a dielectricmultilayer board having a topological metallization pattern on its faceside and through holes electrically connecting the chip bonding pads tothe topological metallization pattern of the board and filled with anelectrically conducting material. The chips are slightly sunk into themetal base, and the planarization of the circuit is attained byapplying, polymer dielectric layers of the board (cf. "Electronicdevices on chip integral circuits", edited by I. N. Vozhenin, 1985,"Radio i Sviaz" Publishers, Moscow, p.261 (in Russian).

The circuit mentioned above is possessed of an inadequate heatconductance and low electrical characteristics.

SUMMARY OF THE INVENTION

The principal object of the present invention is to provide a powermicrowave hybrid integrated circuit having such a constructivearrangement that allows to improve electrical and heat dissipatingcharacteristics thereof.

The foregoing object is accomplished due to the fact that in a powermicrowave hybrid integrated circuit, comprising a metal base havingrecesses, naked semiconductor chips disposed in and fixed to saidrecesses with a binder, a dielectric board having, a topologicalmetallization pattern on its face side and holes electrically connectingthe chip bonding pads to the topological metallization pattern of theboard and filled with an electrically conducting material, according tothe invention, the depth of the recesses in the metal base is selectedso that the face surface of the chip and the metal base are coplanar,the dielectric board has a shield grounding metallization on the backside thereof at the places adjoining the metal base, the metal base issealingly joined and electrically connected to the shield groundingmetallization of the board, and the interconnecting holes are sealinglyfilled with an electrically conducting material, the spacing between theside surface of the chips and the side surfaces of the recesses in thebase being of 0.001 to 0.2 mm.

The chip bonding pads to be grounded may be electrically connecteddirectly to the shield grounding metallization of the board through beamleads 0.002 to 0.1 mm high.

The beam leads may be formed on the back side of the board.

Locating the chip face surface and the surface of the metal basecomplanar, providing the shield grounding metallization and sealinglyelectrical connection of the metal base to the shield groundingmetallization, as well as filling, the interconnecting holes in theboard with an electrically conducting material, ensures a hermeticsealing of the semiconductor chips.

Limiting the spacing between the chip side surface and the side faces ofthe recesses in the base from below is dictated by irregularities of themating surfaces, while the upper limit thereof is dictated by conditionsof heat dissipation from the chip.

Connecting the chip bonding pads to be grounded, directly to the shieldgrounding metallization ensures for the shortest possible grounding wireleads and hence their low spurious inductance.

The lower limit of the length of the beam leads is dictated by a minimumheight required for electrical connection of the board to the chipbonding pads, while the upper limit thereof is dictated by the fact thata further increase in the length of the leads is a complicated taskwhich is quite inexpedient.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by a detailed description of aspecific exemplary embodiment thereof to be taken with reference to theaccompanying drawings, wherein:

FIG. 1 is a sectional view of the filed power microwave hybridintegrated circuit; and

FIG. 2 is a plan view of FIG. 1.

BEST METHOD OF CARRYING OUT THE INVENTION

The filed power microwave hybrid integrated circuit, according to theinvention, comprises a metal base 1 (FIG. 1) having a recess 2 of, e.g.,0.60×0.55×0.35 mm. Naked semiconductor chips 3, such as transistor3π6035 of 0.5×0.45×0.3 mm, are placed in and fixed to the recesses 2with a binder 4, e.g., the eutectic Au--Si hard solder. A dielectricboard 5 made of, e.g., Polycor or sapphire being, e.g. 0.5 or 0.25 mmthick has a topological metallization pattern 6 (FIGS. 1 and 2) with,e.g., the following structure: Ti (0.002 μm)--Pd (0.2 μm)--Au (3 μm).Holes 7 (FIG. 1) in the board 5 having a diameter of, e.g., 100 mminterconnect bonding pads 8 of the chips 3 to a topologicalmetallization pattern 6 of the board 5. The holes 7 in the board 5 arefilled with an electrically conducting material 9, by, e.g., being grownsealingly with Pd--Ni (0.2 μm)--Cu (48 μm)--Ni (0.5 μm)--Au (3 μm)applied by the electroplating technique, or filled with a W--Cupseudoalloy, followed by nickel--(0.5 μm) and gold (3 μm)-plating.

The bonding pads of 8 of the chips 3 to be grounded, e.g., transistorsources, are electrically connected directly to a shield groundingmetallization 10 provided on the back side of the board 5. To provideelectric contact of the bonding, pads 8 of the chips 3 to the material 9filling the holes 7 or to the shield grounding metallization 10, 30 μmhigh beam leads 11 are made on the bonding pads 8 by the electrochemicaldeposition of Ni--Cu--Ni (0.5 μm)--Au (3 μm). The beam leads 11 may bemade on the back side of the board 5.

The proposed depth of the recesses 2 in the metal base 1 ensures:

first, an increased area of contact of the chip 3 with the metal base 1and the heat conducting binder 4, thus improving the heat dissipatingcharacteristics of the circuit, according to the invention;

second, short electrical connections of the bonding pads 8 to begrounded, to the shield grounding metallization 10, thus reducingspurious inductance of the beam leads 11 and improving the electricalcharacteristics of the circuit, according to the invention.

The sealing and electrical connection of the shield Groundingmetallization 10 of the board 5 to the metal base 1 ensures the hermeticsealing of the chip 3 and grounding of the shield groundingmetallization 10 and through it, grounding of the bonding, pads 8 of thechip 3, as well as of other circuit components by the shortest route,thus reducing spurious inductance and improving the electricalcharacteristics of the circuit, according to the invention.

Providing electrical connections between the topological metallizationpattern 6 of the board 5 and the bonding pads 8 of the chips 3 throughthe hole 7 sealingly filled with the electrically conducting material 9ensures the protection of the chip 3 and simultaneously the shortconnection length, thus reducing spurious inductance.

The height of the beam leads 11 below 0.002 mm might result inpreventing the shorting, of the metallization of the chip 3 through themetallization of the board 5 when the metallization of the chip 3 is notdielectrically passivated, while their height above 0.1 mm isinexpedient as involving larger dimensions and extra-consumption ofmaterials.

The filed power microwave hybrid integrated circuit used as, e.g., atransistor amplifier, or a packaged semiconductor device, such astransistor, functions as follows.

A signal is applied to the input of the circuit and is then subjected toan appropriate conversion, whereupon the converted (e.g., amplified)signal is picked off the circuit output. Heat released during theoperation of active semiconductor devices, such as transistors, isdissipated through the metal base 1, the board 5, and the beam leads 11.

Thus, the filed circuits ensures:

first, increasing, the area of contact with the base and hence improvingthe heat-dissipating, characteristics;

second, reducing the connection length of the grounding conductors andhence decreasing spurious inductance of the circuit, thereby improvingthe electrical characteristics thereof

Additionally, the circuit is hermetically scaled, whereby it can be usedwithout additional encapsulation, as, e.g., a packaged hybrid integratedcircuit, or a packaged transistor.

In describing the disclosed embodiments of the present invention,specific narrow terminology is resorted to for the sake of clarity.However, the invention is not restricted to the specific terms soselected, and it should be understood that each such term covers allequivalent elements functioning in a similar way and used for solvingsimilar problems.

Although the present invention has been described herein with referenceto the preferred embodiment, it will be understood that variousmodifications and alterations may occur to the details of constructionwithout departing from the spirit and scope of the invention, as will bereadily understood by those skilled in the art.

All these modifications and alterations shouldl be considered to remainwithin the limits of the spirit and scope of the invention and theclaims that follow.

Industrial Applicability

The present invention can be used in semiconductor microelectronics.

What is claimed is:
 1. A power microwave hybrid integrated circuit,comprising a metal base (1) having recesses (2), naked semicinductorchips (3) disposed in and fixed to the recesses (2) with a binder (4), adielectric board (5) having a topological metallization pattern (6) onits face side and holes(7) electrically connecting bonding pads (8) ofthe chips (3) to the topological metallization pattern (6) of the board(5) and filled with an electrically conducting material (9),CHARACTERIZED in that the depth of the recesses (2) in the metal base(1) is selected so that the face surface of the chip (3) and metal base(1) are coplanar, the dielectric board (5) has a shield grounding,metallization (10) on the back side thereof at the places adjoining themetal base (1), the metal base (1) is sealingly joined and electricallyconnected to the shield grounding metallization (10) of the board (5),and the interconnecting holes (7) are sealingly filled with anelectrically conducting material (9), the spacing between the sidesurface of the chips (3) and the side surfaces of the recesses (2) inthe metal base (1) being, of 0.001 to 0.2 mm.
 2. The power microwavehybrid integrated circuit as set forth in claim 1, wherein the bondingpads (8) of the chips (3) to be grounded are electrically connecteddirectly to the shield grounding metallization (10) of the board (5)through beam leads (11) 0.002 to 0.1 mm high provided on the bondingpads (8) of the chips (3).
 3. The power microwave hybrid integratedcircuit as set forth in claim 1 wherein the beam leads (11) are locatedon the back side of the board (5).